Speed up loading of the "Users Assigned to Set" page.

Load all user sets for the given set and all users before rendering the
template instead of getting one set at a time in the for loop inside the
template.  This speeds up loading of this page a lot with a large number
of users.  With 5000 users it decreases the load time from 3.4 seconds
to 0.14 seconds.

Author: drgrice1

lib/WeBWorK/ContentGenerator/Instructor/UsersAssignedToSet.pm

@@ -33,6 +33,10 @@ sub initialize ($c) {
 	my $setID = $c->stash('setID');
 	my $user  = $c->param('user');
 
+	# Make sure these are defined for the template.
+	$c->stash->{user_records} = [];
+	$c->stash->{set_records}  = {};
+
 	# Check permissions
 	return unless $authz->hasPermissions($user, "access_instructor_tools");
 	return unless $authz->hasPermissions($user, "assign_problem_sets");
@@ -62,7 +66,7 @@ sub initialize ($c) {
 	}
 
 	# Get all user records and cache them for later use.
-	$c->{user_records} =
+	$c->stash->{user_records} =
 		[ $db->getUsersWhere({ user_id => { not_like => 'set_id:%' } }, [qw/section last_name first_name/]) ];
 
 	if ($doAssignToSelected) {
@@ -71,7 +75,7 @@ sub initialize ($c) {
 
 		my %setUsers = map { $_ => 1 } $db->listSetUsers($setID);
 		my @usersToAdd;
-		for my $selectedUser (map { $_->user_id } @{ $c->{user_records} }) {
+		for my $selectedUser (map { $_->user_id } @{ $c->stash->{user_records} }) {
 			if (exists $selectedUsers{$selectedUser}) {
 				unless ($setUsers{$selectedUser}) {    # skip users already in the set
 					debug("saving $selectedUser to be added to set later");
@@ -89,6 +93,8 @@ sub initialize ($c) {
 		}
 	}
 
+	$c->stash->{set_records} = { map { $_->user_id => $_ } $db->getUserSetsWhere({ set_id => $setID }) };
+
 	return;
 }
 

templates/ContentGenerator/Instructor/UsersAssignedToSet.html.ep

@@ -41,9 +41,9 @@
 				</tr>
 			</thead>
 			<tbody class="table-group-divider">
-				% for my $user (@{ $c->{user_records} }) {
+				% for my $user (@$user_records) {
 					% my $userID  = $user->user_id;
-					% my $userSet = $db->getUserSet($userID, $setID);
+					% my $userSet = $set_records->{$userID};
 					%
 					<tr>
 						<td class="text-center">